The meaning of txpowmax AND txpower



  • Hello.
    Whats the meaning of both txpowmax and txpower can I control them by sysctl? I've got three CM9 on a PC all the tree have the same txpower but the txpowmax is different in every one. Why?

    
    $ ifconfig -v ath0
    ath0: flags=8843 <up,broadcast,running,simplex,multicast>mtu 1500
    	inet6 fe80::20b:6bff:fe4d:569d%ath0 prefixlen 64 scopeid 0x3 
    	inet 192.168.6.1 netmask 0xffffff00 broadcast 192.168.6.255
    	ether 00:0b:6b:4d:56:9d
    	media: IEEE 802.11 Wireless Ethernet autoselect mode 11a <hostap,turbo>status: associated
    	ssid CASALDAVELHA channel 58 (5290) bssid 00:0b:6b:4d:56:9d
    	authmode OPEN privacy OFF deftxkey UNDEF powersavemode OFF
    	powersavesleep 100 txpowmax 32 txpower 63 rtsthreshold 2346
    	mcastrate 1 fragthreshold 2346 -pureg protmode OFF -wme burst
    	ssid SHOW -apbridge dtimperiod 1 bintval 100
    
    $ ifconfig -v ath1
    ath1: flags=8843 <up,broadcast,running,simplex,multicast>mtu 1500
    	inet6 fe80::20b:6bff:fe34:9ff9%ath1 prefixlen 64 scopeid 0x4 
    	inet 192.168.4.1 netmask 0xffffff00 broadcast 192.168.4.255
    	ether 00:0b:6b:34:9f:f9
    	media: IEEE 802.11 Wireless Ethernet autoselect mode 11g <hostap>status: associated
    	ssid wireless channel 6 (2437) bssid 00:0b:6b:34:9f:f9
    	authmode OPEN privacy OFF deftxkey UNDEF powersavemode OFF
    	powersavesleep 100 txpowmax 40 txpower 63 rtsthreshold 2346
    	mcastrate 1 fragthreshold 2346 -pureg protmode OFF -wme burst
    	ssid SHOW -apbridge dtimperiod 1 bintval 100
    
    $ ifconfig -v ath2
    ath2: flags=8843 <up,broadcast,running,simplex,multicast>mtu 1500
    	inet6 fe80::20b:6bff:fe36:bf8d%ath2 prefixlen 64 scopeid 0x5 
    	inet 192.168.9.1 netmask 0xffffff00 broadcast 192.168.9.255
    	ether 00:0b:6b:36:bf:8d
    	media: IEEE 802.11 Wireless Ethernet autoselect mode 11a <hostap,turbo>status: associated
    	ssid SARRADA channel 42 (5210) bssid 00:0b:6b:36:bf:8d
    	authmode OPEN privacy OFF deftxkey UNDEF powersavemode OFF
    	powersavesleep 100 txpowmax 32 txpower 63 rtsthreshold 2346
    	mcastrate 1 fragthreshold 2346 -pureg protmode OFF -wme burst</hostap,turbo></up,broadcast,running,simplex,multicast></hostap></up,broadcast,running,simplex,multicast></hostap,turbo></up,broadcast,running,simplex,multicast> 
    


  • CM9 have diferent TX power depending on the band you're using (802.11a/b/g) and also depending on the rate that is transmiting.



  • If you look at your card spec. you will see why it is like this:

    Example spec.

    @54mbit A output = 13dbm
    @6mbit A output = 18dbm
    etc. etc.

    Then dbi to mw:
    13dbm = 20mw
    18dbm = 63mw

    so txpower = max power the card can handle.
    txpowmax = max output in current mode.


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